The application claims priority to U.S. Provisional Application No. 60/560,206, filed on Apr. 7, 2004.
This invention relates to a compass and, more particularly, to an electronic compass assembly and methods for controlling and calibrating an electronic compass assembly.
Electronic compass assemblies are often used in vehicles to indicate to a driver or passenger of the vehicle the direction that the vehicle is facing or traveling. A typical electronic compass assembly includes magnetic sensors that detect the magnetic field of the Earth. A microprocessor typically then calculates the direction of the vehicle from the detected magnetic field and displays the direction as one of North, South, East, West, Northeast, Northwest, Southeast, and Southwest.
Typical electronic compass assemblies are periodically calibrated to account for magnetic interference, drift in the magnetic sensors over time, and other factors that affect the accuracy of the calculated direction. The microprocessor requires magnetic field data through a 360° rotation (or a predetermined percentage of the 360° turn) of the vehicle to perform the calibration. Magnetic field data is collected and stored until the vehicle undergoes the full 360° rotation (or a predetermined percentage of the 360° turn).
Often, the vehicle travels for a considerable period of time and over a considerable distance before completing a 360° rotation (or a predetermined percentage of the 360° turn) and acquiring a sufficient set of magnetic field data to perform the calibration. Magnetic field data collected over long time periods or over long distances may skew the calibration. The microprocessor clears the stored magnetic field data if a timeout period is exceeded in order to assure that magnetic field data used for the calibration is reliable. Disadvantageously, the timeout period may occur just as the microprocessor is about to begin the calibration. Upon clearing the stored magnetic field data, the microprocessor begins collecting and storing all new magnetic field data without having performed the calibration. This may result in an extended period of time between calibrations and inaccurate calculation of the direction of the vehicle.
Accordingly, there is a need for an electronic compass assembly and method that reliably calibrates more often to provide more accurate calculations of vehicle directions. This invention addresses those needs and provides enhanced capabilities while avoiding the shortcomings and drawbacks of the prior art.